This project is part of a general program to use specific antibodies as tools to study the chemical basis and biosynthetic origins of native protein conformation. Purified neurophysin antibodies have been used to identify biosynthetic precursors of neurophysins (and the closely associated peptide hormones oxytocin and vasopressin) which are produced in cell-free synthesis in the presence of bovine hypothalamic mRNA. The nature of recognition of neurophysins and precursors with the purified antibodies is being studied. Antibodies prepared against thermolysin and two large fragments of this protein have been used in immunodiffusion assays and radioimmunoassays to study conformational properties of the native protein as well as the fragments. Affinity chromatographic techniques have been used to isolate ribonuclease antibodies specific for the S-peptide region (residues 1-20). Competition radioimmunoassay experiments are being carried out to determine the precise specificity of the antibodies and to try to use these to design semisynthetic proteins with altered antigenicity.